An estimated 5 million to 8 million animals are euthanized in shelters across this country every year. Many organizations are trying to decrease that number by opening low-cost spay/neuter clinics that will prevent more litters of cats that need homes. One such organization is LifeLine Animal Project, an Atlanta-based nonprofit shelter and clinic where more than 25,000 spay/neuters have been performed since 2005. WebMD talked to executive director Rebecca Guinn to find out about some spay-neuter myths and facts.

Q: Why should I have my cat spayed or neutered?

A: Shelter euthanasia is the number one killer of companion animals, and spaying and neutering is the only way to reduce or eliminate that. It's also better for your pet's health. And it's better for you because it will make your life easier if your pet is spayed or neutered.

There's also a financial side. It varies by community, but it's about $100 for animal control to impound and euthanize a cat. Just in the Atlanta area alone, more than $15 million in tax dollars is spent annually dealing with stray and unwanted pets.

Q: Shouldn't I let my cat have a litter before I spay her?

A: No. You shouldn't for several reasons. It greatly reduces the risk of certain cancers if you have her spayed before the first heat and certainly before she has a litter.

And most places are overrun with kittens, particularly in the south. Overrun. And there is simply no excuse whatsoever to allow your cat to have kittens. There are millions of cats and kittens out there that need homes and millions more that are abandoned or handed out at places like Wal-Mart. There's simply no good argument to have a litter of kittens.

There are shelters in the Atlanta area that can have 40 to 50 moms with litters in their shelters on any given day during the spring and summer. There simply aren't enough homes for all the cats that get born every kitten season. And in the south, kitten season is almost year round. And there's a kitten season everywhere.

Q: Should I let my cat have a heat before I spay her?

A: There's no reason to do that. It's a myth that animals should have a litter first or a heat before they are spayed. There are no health benefits to that at all, and it's a much easier medical procedure if you spay before the first heat. All the benefits you get from spaying or neutering your pet are magnified by spaying or neutering before the animal reaches puberty.

Q: Is it OK to spay my cat when she's just a kitten?

A: Yes, as long as she's at least eight weeks of age and weighs at least eight pounds. Pediatric spay/neuter is widely accepted. Those ideas about needing to wait are really antiquated and the evidence is to the contrary. Even the American Veterinary Medical Association supports early spay/neuter.

And cats can go into heat very early. They can have a litter at six months of age, and they can have three litters a year. Also, if you've ever been around a cat in heat, you know it's miserable for people. They yowl loudly and continuously. They want to get out. It really alters their behavior. And every unneutered male cat in the neighborhood will be at your house spraying the outside of your house, spraying your front door, spraying under your crawlspace. Your whole house will reek of cat spray. It is a really, really regrettable experience.

Q: It can cost more than a $100 to get a cat spayed or neutered. I can't afford that. What can I do?

A: There are a lot of low-cost options all over the country. The ASPCA keeps a database of low-cost options on its web site, where you can put in your zip code and it will give you all your options within a certain radius of your zip code. It's at aspca.org. Click on the “pet care” tab and look for the low-cost and free spay/neuter database.

here usually are more low-cost options for cats than there are for dogs. That's because it's a much easier procedure in cats than in dogs. At our clinic, we neuter cats for $35 and spay cats for $45. There are some clinics that do nothing but cats. So there are a lot of options available for cats.

Q: Don't cats get fat once you spay or neuter them?

A: It goes back to portion control and exercise. I recommend cats be kept indoors, and you have to have enough environmental enrichment to keep your cat happy. So have vertical spaces, climbing trees, things like that. Have places where they can hide, places where they can play, places where they can just be cats. But portion control is the main thing. If you have a cat that won't stop eating, don't free feed your cat. That's something you can control and have a responsibility to control.

Q: There's a statistic that says one unspayed female cat can lead to 420,000 cats. Is that true?

A: Stray cats are a huge problem. But it's not close to half a million cats per female. If it were, we'd be hip deep in cats.

Technically, I suppose it's possible. But it assumes that the cats are having the largest possible litters, that all the kittens survive, and that everything goes along just fine and none of the cats ever die or are altered. But that's just not the reality.

Obviously, many cats are spayed or neutered. And stray or feral cats, free roaming cats, don't have that kind of survival rate for kittens. It's more like 25% to 40% survive. Those figures have been examined and they just don't hold up. It's more like an unspayed female can lead to 100 more cats out there, which is still too many. But it's not that crazy number. That's not realistic.

Q: Will my tomcat stop running away from home if I neuter him?

A: We don't recommend having free-roaming cats. And if you have an unaltered male cat, you're probably not seeing much of him anyway.

Usually, neutering a tom will curb its desire to roam, although cats are a little different than dogs and wander for reasons other than reproducing, such as hunting. So neutering will reduce the instinct to roam, but it won't eliminate it.

Unaltered males also are more at risk for feline leukemia [FeLV] and FIV [feline immunodeficiency virus]. That's because they fight, and deep bite wounds are the leading factor in the transmission of those diseases.

Q: My cat sprays all over my house. If I neuter him, will that stop?

A: More than likely it will. It will certainly take away that hormonal urge to spray. Neutering early is your best bet to avoid that urge altogether. If you have a neutered cat that is still spraying, you should see your veterinarian. It could be a behavioral issue, or it could be a health problem. But the first step in controlling spraying or marking territory is neutering.

Q: Will spaying or neutering my cat prevent future illnesses?

A: You'll have a lower incidence of mammary tumors. We see a lot of unspayed cats come into our clinic with pyometra (an infection of the uterus), which can be a life-threatening disease for them.

For male cats, you eliminate testicular diseases, and for females, you eliminate the risk of uterine diseases. Generally, spayed and neutered pets live longer, happier lives.